The present invention relates to apparatus for linearizing the output of a condition sensing bridge circuit and, more particularly, to the linearization of the Honeywell Microbridge Mass Airflow Sensor, forms of which are described in patents such as U.S. Pat. Nos. 4,472,239, 4,478,076, 4,478,077, 4,501,144, 4,548,078, 4,581,928, 4,624,137, 4,651,564 and 4,739,657.
The Honeywell Microbridge Mass Airflow Sensor includes a wheatstone type bridge in which first and second sensing resistors are located in a flow stream on opposite sides of a heater element. The upstream sensor will lose some of its heat into the air stream and the downstream sensor will receive additional heat from the air stream due to the heater element. The temperatures of the sensors and thus their resistances will change with changes in the mass airflow of the stream to unbalance the bridge and the output of the bridge will accordingly be indicative of mass airflow.
A difficulty encountered in the present device is the fact that the output varies in a non-linear fashion with respect to the airflow, and this is undesirable for many applications.